Charles e



(No Model) G. E. CARPENTER.

ELECTRIC HEATING APPARATUS.

No. 415,856. 7 I Patented Nov. 26, 1889.

n. PETERS. Pholoixlhogmphcr. Washington. a c.

UNITED STATES PATENT OFFICE.

CHARLES E. CARPENTER, OF'MINNEAPOLIS, MINNESOTA, ASS IGNOR OF FOUR-SIXTHS TO F. V. NEVENS AND JNO lV. KELLY, BOTH OF SAME PLACE;

ELECTRIC H EATING APPARATUS.

W SPECIFICATION forming part of Letters Patent No. 415,856, dated November 26, 1889.

Application filed August 6, 1889. Serial No. 319,960. (No model.)

To all whom it may concern:

Be it known that 1, CHARLES E. CARPENTER, acitizen of the United States, residing in the city of Minneapolis, in the county of'Hennepin and State of Minnesota, have invented certain new and useful Improvements in Electro- Heating Apparatus, of which the followingis a specification.

This invention relates to improvements in eleetro-heating apparatus in which heretofore a carbon resistance has been employed for heating the body by which it is inclosed. This method, however, is objectionable, not only because of the great expenseinvolvedin the use 1 I 5 of the carbon resistanoe,but also because of the liability to short-circuiting, the inequality in the distribution of heat, and the constant danger of fracture thereof due to concussions to which the body is subjected, especiallyif of a movable form-such as a sad-iron, foot-rest,

or other usual form of device to which electro-heating apparatus is attachedas a result of which the utensil would immediately become useless and would require complete dis- 2 5 connection and the substitution of a new resistance, thereby involving both time and expense.

The object of this invention is to utilize economically the heating effects produced by passing acurrent of electricity through a conductor of high resistance and low capacity for the purpose of heating stoves, laundry machinery, and sad-irons, and similar utensils, by producing heat in and confining it to such part or parts only of the utensil as is desirable.

Another object is to prevent the heat thus developed from being transmitted either by conduction or radiation to other parts of the same body or to other bodies than those it is desired to heat, and to combine in the maximumdegree in an electro-heating apparatus cheapness, durability, compactness, and simplicity of construction.

A further object is to have a metallic resistance, and of such character that it may not only be readily and quickly attached to and detached from the utensil, but may be conformed to any desired configuration of surface to be heated, and so arranged as to operate directly upon and uniformly heat all parts of the surface; and,finally, to dispense withithe necessity for chambering or grooving the body of the utensil for receptionof the resistance, which has heretofore been found necessary by reason of the peculiar character of the resistance employed, as a result of which the utensil cannot be heated uniformly throughout or near the edges thereof, and to have a resistance of such a character that no chamberi'ng is required, and which cannot be fractured when once in its operative position.

These objects are attained by the devices illustrated in the accompanying drawings, in whic h Figure 1 represents a plan view of a cook ing-stove embodying my invention; Fig. 2, a similar view showing the top or heating plates of the stove removed, more clearly disclosing the arrangement and disposition of the resistance to these said plates; Fig. 3, an enlarged transverse section 011 the line 3 3 of Fig. I. Fig. 4 illustrates the application of my invention to a laundry or-other heating roller, and Fig. 5 its application to a sad-iron.

1 Similar letters of reference indicate the same parts in the several figures of the drawings.

My invention broadly consists in interposing between the surface-plate to be heated and the body supporting the same a reflex metallic resistance, between which and the surface to be heated lies an electric insulator, and between which and the body lies an electric insulating non-conducting heat material for confining the heat to the surface-plate. This general construction is applicable to numerous forms of apparatus and utensils, regardless of their shape or contour, and I have therefore illustrated in the drawings only the more common forms of utensil for which my invention is especially adapted, and which are sufficient to disclose the adapt ability thereof to various uses.

Referring now in general terms to the construction common to all of the forms illustrated in the drawings, let A represent the main body, whether stove, roller, or sad-iron,

or any other desirable form of utensil, and B the surface-plate to be heated, secured together by means of screws G, or in any other well-known and convenient manner, between which are interposed, first, a sheet of asbestus cloth or card-board D, or any other suitable electric insulating non-heat-conducting substance lying next to the body of the utensil, to the opposite or outer surface of which is secured the metallic resistance E, consisting of wire of a refractory character reflexed back and forth over the surface of the asbestus sheet, as illustrated in Fig. 2, and preferably secured thereto by any convenient form of fasteningsuch as sewing with an asbestus thread, staples, and numerous other devices well known in the arts. This metallic resistance is separated from the'surface to be heated by another sheet F, of substantially the same size and contour as the sheet D, composed of some electrical insulating substance which is non-combustible and ofjust sufficient thickness to prevent the wires or other material used as a resistance from coming into contact with the surface-plate to be heatedsuch, for instance, as very thin asbestus paper, mica, or any other material that fulfills the above requirements-it being understood that this sheet F, while a nonconductor of electricity, should be a fairly good conductor of heat, while the sheet D, on the contrary, should be not only an electric insulator, but a non-conductor of heat, for which reason I prefer that the sheet D should be of thick asbestus and the sheet F of thin mica.

The body A is preferably recessed immediately back of the insulating-sheet D to any desired deptlnleaving only thin walls around the sides thereof, which recess is filled with a packing G, of asbestus felt, mineral wool, or some other substance which is a non-conductor of heat, and which, in conjunction with the asbestus sheet D, lying behind the resistance-Wires, acts as an insulator for the heat evolved from the resistance, and almost perfectly confines the heat to the surface-plate, preventing it from being wasted in the atmosphere or being conducted to bodies other than those it is desired to heat; and from the construction described it will readily be seen that while the dissipation of heat by radiation is prevented by this layer and packing of asbestus or other non-conducting material its transmission and conduction and dissipation are likewise almost wholly prevented by reason of the only metallic connection between the heated surface-plate and the body of the utensil being the screws or other devices by which they are united together, the asbestus and mica layers interposing therebetween at all points.

The use of a wire of a refractory metal as the heat-generating resistance is preferred, because a large amount of wire can be applied, so as to almost completely cover a surface without any part of the wi re coming into contact with any other adjacent part of the same or other wire, and, being rcflexed, prevents self-induction when used with an alternating current; besides which itis well known that the resistance to the passage through any surface or to any configuration upon a' surface which may be desirable.

Referring now more particularly to the specific applications of my invention illustrated in the drawings, I will first describe the detailed construction of a stove embodying my invention. (Illustrated in Figs. 1, 2, and In this as in all other special appliances, the common features existnamely, the body A, surface-plate B, the resistance E, the electric insulating but non-heat-conducting sheet D, and the electric insulating-sheet F between the resistance and the surface-plate; but in this construction the surface-plate is preferably divided into a series of sections II, the meeting edges of which are beveled, as shown, so as to reduce the area of the metallic contacting surfaces to the minimum, and thus correspondingly reduce the conduction of heat from section to section, and each of which may be heated independently of the other or while the others are in a warm or cold condition; or, if desired, the sections ll may be subdivided into smaller sections I, each of which is likewise arranged to be heated independently of the other and having the same general rectangular shape, but of less dimensions than sections H. Still further divisions of the sections may be made by the employment of the circular detached plates J, fitting within corresponding openings in the main plate and sustained therein by radial lugs or projections K, resting upon and corresponding with recesses in the main plate, or in any other convenient manner.

Each of the sections H, I, and J has a resistance or resistances connected with the source of electrical energy independently of all of the other sections, one form of disposing of the resistance and their connection with the line-wires L M being illustrated in the diagram view of Fig. 2. For instance, the section H is provided with two independent resistances, but both con nectcd with the same source of supply, the resistance being thus arranged in multiple arc, and, although separate, operate simultaneously to uniformly heat the entire plate. I11 the plates I the resistances are shown as connected in independent series for each plate, while in the circular plates J two are shown as provided with operation; or, if desired, all of the resistances of the stove, and by reason of their flexibility .illustrated in Fig. 5 are the principal eleposition of the resistance-wires between the independent resistances similar to the plate l H, and the other with the resistances in series similar to those of the plates I. The resistance ofthese sections may be controlled by a switch-board of any desirable form such as is well known in the art to which this invention appertains, for connecting all of the resistances of the section either in series or multiple arc, and for cutting out one or more of the sections while the remainder are in of all of the sections may be thrown into a single series or any other desired combination for producing a desired result, such as the warming of all of the plates or regulating the temperature thereof to any desired degree.

Referring now to the heating-roller illustrated in Fig. 4, the electro-heating apparatus is identical in every respect with that of the stove illustrated in Figs. 1, 2, and 3, in so far as relates to the arrangement of the heating surface-plate body and the insulating materials thereof, as well as the disinsulating-sheets, the only difference being in the manner of disposing of the terminals of the resistance and line wires, which in this case must be adapted to make constant contact between a moving and a stationary surface, which, however, may be readily accomplished by having the terminals suitably insulated and connected, respectively, with the insulated metallic rings 0 P, mounted upon the hub of the roller, against which bear metallic brushes Q R, with which connect the terminals L M of the line-circuit from the source of electrical energy. The general contour of this roller, while cylindrical and differing materially from the flat surface of the stove, may be heated in exactly the same manner, the resistance-wires being reflexed over the surface thereof, just as in the case readily conform to the contour of the roller without afiecting its function as a resistance in theleast degree. So, also, with the flat-iron ments of my invention disposed and arranged in substantillly the same manner as in the constructions previously described, the surface-plate thereof, however, being continuous, as best adapted to the work to be performed, and the resistance being refiexed and arranged in a suitable manner to cover substantially all of the surface-plate, notwithstanding its irregular contour. In this case the terminals of the resistance pass upwardly through the body of the iron to binding-posts S, mounted upon an insulating-block attached to the iron, with which engages a metallic spring-coupling [,of any desired form, to which the terminals of the line-circuit are attached, this coupling serving as a means for readily detaching the iron from the linewire, and thereby cutting it out of the circuit.

The shell or body of the various devices to which my invention is applied is of just sufficient thickness to withstand mechanical injury and still form a rigid structure, the corners, ends, or any intermediate portions thereof being made somewhat thicker than the other portions of the shell to accommodate the screws which fasten to it the removable heating surface-plate.

By the employment of a reflexed wire resistance, as described, the heat may be directed to and confined at the very edges of the surface-plate to be heated, thus making all portions thereof of a uniform temperature, and when the resistance is fastened to the detachable sheet or card a further advantage is gained by the readiness with which the resistance may be changed to suit any voltage of current by simply taking out one card with its wires and substituting another with more or less resistance, as required, which is of especial importance where it becomes necessary to change the source of electrical energy, for in all other devices of this class, so far as I am aware, the utensil would have to be changed or reconstructedwith very material change in the electrical pressure.

An apparatus constructed in accordance with my invention combines in the maximum degree, cheapness, durability, and simplicity, possessing all of the advantages and none of the disadvantages common to electric heating apparatus as heretofore employed, besides having advantages possessed by no other electric heating apparatus, all as fully hereinbefore set forth.

Having described my invention, What I claim, and desire to secure by Letters Patent, 1s-

1. In an electro heating apparatus, the combination, with the body and the heating surface-plate thereof, of an electrical resistance lying between said body and plate, a layer of electrical insulating material between said resistance and the plate, and a layer of electrical insulating non-heat-conduct-ing material between said resistance and the body, substantially as described.

2. In an electro heating apparatus, the combination, with the body and the heating surface-plate thereof, of an electrical resistance, consisting of a refiexed refractory wire lying bet-ween said plate and body, a layer of electrical insulating material between said resistance and plate, and a layer of electrical insulating but non-heat-conducting material between said resistance and the body, substantially as described. I

3. In an electro heating apparatus, the combination, with the body recessed on the outer face thereof and the heating surfaceplate covering said recess, of a packing of incombustible non heatconducting material filling said recess, an electrical resistance lying between said body and plate, a layer of electrical insulating but non-heat-conductin g material interposed between said resistance and the body, and a layer of electrical insulating materialinterposed between said resistance and the heating-plate, substantially as described.

4. In an electro heating apparatus, the combination, with the body and the removable heating surfaceplate, of a detachable layer of electrical insulating and non-heatconducting material between said body and plate, an electrical resistance consisting of a refractory refiexed wire attached to and removable with said layer, and a layer of electrical insulating material between said resistance and the removable heating-plate, substantially as described.

5. In an electro heating apparatus, the combinatiomwith the body and the sectional heating surface-plate thereof, of a series of independent electrical resistances underlying the sections of said plate,a layer of electrical insulating material between said resistances and the plate, and a layer of electrical insulating non-heat-conducting material betweensaid resistances and the body, substantially as described.

6. In an electro heating apparatus, the co1nbination,with the body and the sectional heating surface-plate thereof, of one or more electrical resistances underlying each section of said plate, a layer of electrical insulating material between said resistances and the plate, and a layer of electrical insulating nonheat-conducting material between said resistances and the body, substantially as described.

CHARLES E. CARPENTER.

Witnesses:

R. C. OMOHUNDRO, W. R. OMOHUNDRO. 

